Metal bending machines comprising a lower pinchroller, an upper pinchroller and a radius roller are known. In such machines, the lower pinchroller is rotatably mounted upon a rigid structure or base, and a means of rotating the lower pinchroller such as a hydraulic motor or a chain drive is applied to one end of the pinchroller. In such machines, the upper pinchroller is suspended above the lower pinchroller in alignment therewith by a mechanism which provides for variable vertical positioning of the upper pinchroller with respect to the lower pinchroller, and which allows rotation of the upper pinchroller. A rotating means such as a hydraulic motor or a chain drive is applied to an end of the upper pinchroller. In operation, the rotating means of the upper and lower pinchrollers counter-rotate. When a metal work piece is inserted into the pinch point between such upper and lower pinchrollers, along a line substantially tangent to the pinchrollers, the counter-rotation pulls the metal workpiece into the pinch point and then drives the workpiece outward from the pinch point on the other side of the pinchrollers along the tangent line.
In order for pinchrollers configured as described above to perform the function of bending a metal workpiece, a radius roller is typically mounted in alignment with the pinchrollers, and positioned so that a metal workpiece being drawn through the pinch point of the pinchrollers comes into contact with the exterior radial surface of the radius roller at a point above the axis of the radius roller. Upon such contact, the metal workpiece is deflected upward. The upward deflection induced by the radius roller causes the metal workpiece to bend at the pinch point. Continued progression of the metal workpiece driven through the pinch point of the pinchrollers and continued upward deflection induced by the radius roller results in a constant bend along the length of the workpiece.
A typical application of metal bending through use of pinchrollers and a radius roller configured as described above is the formation of a tubular pipe section from flat sheet metal. A piece of rectangular sheet metal may be driven through the pinch point and deflected upward over the radius roller until the metal curls back upon itself in a circle. Upon removal of the curled metal workpiece from the machine, the ends of the workpiece may be welded to each other to form a cylindrical pipe section.
Pinch rolling metal bending machines as described above typically are useful only for bending sheet metal and substantially flat metal bars. Tubular metal and metal configured as an angle iron, a channel iron, or an I-beam which is driven through pinchrollers and over a radius roller as configured above are subject to crushing deformation and spiral out of plane bending. To eliminate the problems of crushing deformation and spiral bending, pinch rolling metal bending machines are known to be "customized" to induce bends upon metal workpieces having various cross-sectional shapes. For example, a pinch rolling metal bender designed to accommodate metal pipes having a circular cross-section would have a lower pinchroller with an annular semi-circular channel closely fitted to the exterior radial surface of the pipe. The upper pinchroller and the radius roller would have a similar annular channel. Each of the three channels are aligned within a common plane. Where the pinchrollers and the radius roller have such specially fitted annular channels, the pinch point matches the cross-sectional shape of the workpiece preventing the compressive force of the pinchrollers from crushing or distorting the workpiece. The workpiece contacts the radius roller within a fitted annular channel assuring that the bend lies within a single plane, rather drifting laterally, causing a spiral bend.
A metal working machine shop may have several pinch rolling metal bending machines in order to bend sheet metal, channel iron, I-beams, and tubular metal of various shapes. Utilizing several machines to perform pinch rolling metal bending upon metal workpieces of varying shapes is uneconomical in terms of money, manufacturing space, and time spent moving from machine to machine. The present invention eliminates these disadvantages by providing a single pinch rolling metal bending machine which may be interchangeably configured to accommodate at one time several types of metal workpieces, including sheet metal, angle iron, channel iron, I-beams, and tubular metal.